Unable to end date/make inactive Annual Leave plan

Summary:

Unable to end date/make inactive Annual Leave plan

Content (please ensure you mask any confidential information):

Hello

We have a number of Annual Leave plans which are no longer in use and we want to hide them from the picklists that appear when assigning plans to employees.

I have checked and there are no employees currently assigned to the plan.

Navigation: setup and maintenance > absence plans > search plan name > enter plan> edit- update > change status to either closed or inactive.

Receive following error message:

You can't delete this master record because a matching detailed record exists.

Is anyone able to advise why this is not working?